Pant structure with efficiently manufactured and aesthetically pleasing rear leg edge profile

ABSTRACT

A disposable absorbent pant having a front belt portion and a rear belt portion is disclosed. The front and rear belt portions are joined at side seams and the rear belt portion has a greater length than the front belt portion. A lower edge of the rear belt portion forms at least in part edges of left and right leg openings to the rear of the side seams. The rear belt portion includes first and second layers of nonwoven web material sandwiching a plurality of laterally extending and laterally pre-strained elastic strands, disposed below the side seams. A first of the plurality of elastic strands differs from a second of the plurality of elastic strands by one or more of amount of pre-strain, tensile modulus, decitex, and combinations thereof.

BACKGROUND OF THE INVENTION

In order to maintain or grow their market share, manufacturers ofdisposable absorbent articles such as disposable diapers and absorbentpants must continue to discover and develop improvements to materials,components and features that affect aspects such as containment,absorbency, comfort, fit and appearance. Absorbent pants aremanufactured in smaller sizes to be used as, e.g., pull-on diapers andtoilet training pants for young children, and in larger sizes to be usedas, e.g., undergarments for persons suffering from incontinence.

A particular type of absorbent pant design currently marketed issometimes called the “balloon” pant. The balloon pant design usuallyincludes a central absorbent chassis and an elastic belt. The elasticbelt is usually relatively wide (in the longitudinal direction) andelastically stretchable in the lateral direction. It entirely encirclesthe wearer's waist, and thereby covers a relatively large amount of thewearer's skin, and also makes up a relatively large portion of thevisible outside surfaces of the pant. The central chassis portion istypically joined to the inside of the belt in the front, wraps under thewearer's lower torso between the legs, and is joined to the inside ofthe belt in the rear. The belt is often formed of two layers of nonwovenweb sandwiching one or more elastic members such as a plurality oflaterally-oriented strands or strips of elastomeric material, or asection of elastomeric film or elastomeric nonwoven. It is common amongsuch designs that, in manufacture, the elastic member(s) are sandwichedbetween the nonwoven web layers in a strained condition. Upon completionof manufacture and allowance of the belt with sandwiched elasticmember(s) to assume a relaxed condition, the elastic member(s) contractlaterally toward their unstrained lengths. This causes the nonwoven weblayers to form gathers that take the form of visible rugosities in thebelt.

The belt structure may be formed of separately formed front and rearportions, joined at seams along the side/hip areas. It may be desired insome circumstances that the front portion have less length (in thevertical direction relative a standing wearer) than the rear portion, toprovide a leg opening that is higher in front to permit easier bodymovement and/or provide less opportunity for rubbing and chafing at thefront leg openings. Conversely, it may be desired that the rear portionhave greater length, to provide greater coverage of the wearer'sbuttocks.

When such front and rear portions of the belt are joined at side seams,however, the leg openings will have step profiles at the seams where thelonger rear belt portion meets the shorter front portion. If acompensating modification is not made, the step profiles may present anawkward or unsightly appearance when the pant is worn. Portions of thematerial along the step profiles adjacent the edges of the leg openingsin the rear may flip or curl and present a ragged, unfinished orhaphazard appearance.

One way in which to address this problem is to cut a curved leg cutoutprofile into at least the rear portion of the belt structure duringmanufacture of the pant. Such cutting, however, adds cost and complexityto manufacturing, by creating a need for the design, fabrication andoperation of efficient cutting equipment for the manufacturing line, asystem for removal of the cutoff scrap from the line equipment and plantenvironment, and a system and/or procedure for either recycling thescrap or disposing of it as waste.

The balloon pant design provides for certain efficiencies inmanufacture, and it is believed that the design may gain popularity.Consequently, a need for alternatives in the design of a belt structurethat address these issues is presented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective view of an example of a balloon pant.

FIG. 2 is a schematic plan view of a balloon pant precursor structure,prior to joining of the front and rear belt portions at side seams,wearer-facing surfaces facing the viewer.

FIG. 3 is a schematic, exploded perspective view of components of a beltportion.

FIG. 4 is a schematic, close-up plan view of an area of a belt portion.

FIG. 5 is a schematic cross section of the area of the belt portionshown in FIG. 4.

FIG. 6 is a schematic side view of a pant.

FIG. 7A is a schematic plan view of a balloon pant precursor structure,prior to joining of the front and rear belt portions at side seams,wearer-facing surfaces facing the viewer.

FIG. 7B is a schematic side view of a pant.

FIG. 8A is a schematic plan view of a balloon pant precursor structure,prior to joining of the front and rear belt portions at side seams,wearer-facing surfaces facing the viewer.

FIG. 8B is a schematic side view of a pant.

FIG. 8C is a schematic side view of a pant.

FIG. 9 is a schematic plan view of a balloon pant precursor structure,prior to joining of the front and rear belt portions at side seams,wearer-facing surfaces facing the viewer.

DETAILED DESCRIPTION OF THE INVENTION

“Cross direction” (CD)—with respect to the making of a nonwoven webmaterial, the nonwoven material itself, a laminate thereof, or anarticle in which the material is a component, refers to the directionalong the material substantially perpendicular to the direction offorward travel of the material through the manufacturing line in whichthe material and/or article is manufactured.

Throughout the present description, a material or composite of materialsis considered to be “elastic” or “elastomeric” if, when a biasing forceis applied to the material, the material or composite can be extended toan elongated length of at least 150% of its original relaxed length(i.e. can extend at least 50%), without rupture or breakage whichsubstantially damages the material or composite, and when the force isremoved from the material or composite, the material or compositerecovers at least 40% of such elongation. In various examples, when theforce is removed from an elastically extensible material, the materialor composite may recover at least 60% or even at least 80% of itselongation.

“Elongation,” used herein to quantify and express an amount oflongitudinal strain imparted to an elastic strand, means: [(strainedlength of the strand−length of the strand before straining)/(length ofthe strand before straining)],×100%. Where the term “pre-strain” is usedto refer to elongation imparted to an elastic strand during manufactureof a belt structure or pant, it refers to elongation, expressed in thesame manner.

“Film” means a macroscopically continuous skin-like or membrane-likelayer of material formed of one or more polymers. “Film” isdistinguished from “nonwoven web” or “nonwoven” in that the latter has aform consisting of a web-like structure of consolidated butpredominately individually distinct fibers. “Lateral”—with respect to apant and its wearer, refers to the direction generally perpendicular tothe wearer's standing height, or the horizontal direction when thewearer is standing.

“Longitudinal”—with respect to a pant and its wearer, refers to thedirection generally parallel to the wearer's standing height, or thevertical direction when the wearer is standing. “Longitudinal” is alsothe direction generally parallel to a line extending from the midpointof the front waist edge, between the leg openings, to the midpoint ofthe rear waist edge of the pant, when the pant structure is separated atthe side/hip seams and laid out unfolded, extended and flat.

With respect to a pant, positional terms such as “lower,” “lowest”,“above,” “below,” “bottom,” etc., and forms thereof, are expressed withrespect to the vertically lowest extent (at the crotch region) anduppermost extent (at the waist edges) of the pant structure along avertical direction, when worn by a standing wearer. With respect to aprecursor structure to the pant, the lowest portions are proximate thelateral axis (axis 100 depicted in the figures) and the highest portionsare proximate the waist edges.

“Machine direction” (MD)—with respect to the making of a nonwoven webmaterial, the nonwoven material itself, or a laminate thereof, refers tothe direction along the material or laminate substantially parallel tothe direction of forward travel of the material or laminate through themanufacturing line in which the material or laminate is manufactured.

“Machine direction bias,” with respect to the fibers forming a nonwovenweb, means that a majority of the fibers, as situated in the web andunstretched, have lengths with machine direction vector components thatare greater than their cross direction vector components.

A “nonwoven” is a manufactured sheet or web of directionally or randomlyoriented fibers which are first deposited and accumulated onto a movingsurface (such as a conveyor belt) and then consolidated and bondedtogether by friction, cohesion, adhesion or one or more patterns ofbonds and bond impressions created through localized compression and/orapplication of pressure, heat, ultrasonic or heating energy, or acombination thereof. The term does not include fabrics which are woven,knitted, or stitch-bonded with yarns or filaments. The fibers may be ofnatural and/or man-made origin and may be staple and/or continuousfilaments or be formed in situ. Commercially available fibers havediameters ranging from less than about 0.001 mm to more than about 0.2mm and they come in several different forms: short fibers (known asstaple, or chopped), continuous single fibers (filaments ormonofilaments), untwisted bundles of continuous filaments (tow), andtwisted bundles of continuous filaments (yarn). Nonwovens can be formedby many processes including but not limited to meltblowing, spunbonding,spunmelting, solvent spinning, electrospinning, carding, filmfibrillation, melt-film fibrillation, airlaying, dry-laying, wetlayingwith staple fibers, and combinations of these processes as known in theart. The basis weight of a nonwovens is usually expressed in grams persquare meter (gsm). “Preexisting,” with respect to a pattern ofapertures on a nonwoven web, the nonwoven web forming a layer of alaminate, means that the pattern of apertures was formed on the nonwovenweb prior to the incorporation of the nonwoven web into the laminate.

“Z-direction,” with respect to a web, means generally orthogonal orperpendicular to the plane approximated by the web along the machine andcross direction dimensions.

Although examples of the structure of the invention are described hereinas used to form the belt of a balloon-type absorbent pant, it will beappreciated that examples may be used to form other components of pants,diapers, other wearable articles, and other products as well.

FIG. 1 depicts an example of balloon-type absorbent pant 10. FIG. 2depicts the precursor structure of the pant in an open configurationlaid out flat and stretched out laterally against elastic-inducedcontraction, wearer-facing surfaces facing the viewer, prior to finalassembly in which front belt portion 22 is joined to rear belt portion23 at seams 24. To form pant 10, the precursor structure may be foldedat or about lateral axis 100 (located at the longitudinal midpoint ofthe precursor structure) with the topsheet 33 facing inward, and thelongitudinal edges of the front 22 and rear 23 belt portions may bejoined at seams 24, forming a pant structure having leg openings 15,front waist edge 34 and rear waist edge 35.

The pant structure may include a belt 20 and a central chassis 30.Central chassis 30 may include any combination of components found inthe absorbent structures of disposable diapers and absorbent pants,including but not limited to a liquid impermeable backsheet 31 formed atleast in part of liquid impermeable web material, a liquid permeabletopsheet 33, an absorbent core structure (not specifically shown), andelasticized barrier cuffs 32. Examples and descriptions of componentsand configurations of a central chassis may be found in U.S. Pat. App.Pub. No. US 2013/0211355, wherein the chassis described includescomponents and features that may be included in central chassis 30. Inthe example shown in FIG. 1, the front portion of belt 20 stops short ofthe crotch region 12 of the pant, at lower edge 21. Central chassis 30may overlie front and rear belt portions 22, 23 to the inside(wearer-facing side) thereof. The outer perimeter 41 of the centralchassis 30 may be defined by the outer perimeter of the liquidimpermeable web material.

Referring to FIGS. 3-5, one or both of front and rear belt portions 22,23 may be formed of layers of nonwoven web 25 a, 25 b, whichrespectively form inner and outer layers. Suitable nonwoven webmaterials that may be useful in the present invention also include, butare not limited to spunbond, spunlaid, meltblown, spunmelt,solvent-spun, electrospun, carded, film fibrillated, melt-filmfibrillated, air-laid, dry-laid, wet-laid staple fibers, and othernonwoven web materials formed in part or in whole of polymer fibers, asknown in the art. The nonwoven web may be formed predominately ofpolymeric fibers. In some examples, suitable non-woven fiber materialsmay include, but are not limited to polymeric materials such aspolyolefins, polyesters, polyamide, or specifically, polypropylene (PP),polyethylene (PE), poly-lactic acid (PLA), polyethylene terephthalate(PET) and/or blends thereof. In some examples, the fibers may be formedof PP/PE blends such as described in U.S. Pat. No. 5,266,392. Nonwovenfibers may be formed of, or may include as additives or modifiers,components such as aliphatic polyesters, thermoplastic polysaccharides,or other biopolymers. Further useful nonwovens, fiber compositions,formations of fibers and nonwovens and related methods are described inU.S. Pat. No. 6,645,569; U.S. Pat. No. 6,863,933; and U.S. Pat. No.7,112,621; and in U.S. patent application Ser. Nos. 10/338,603;10/338,610; and 13/005,237.

The individual fibers may be monocomponent or multicomponent. Themulticomponent fibers may be bicomponent, such as in a core-and-sheathor side-by-side arrangement. Often, the individual components comprisepolyolefins such as polypropylene or polyethylene, or their copolymers,polyesters, thermoplastic polysaccharides or other biopolymers.

According to one example, the nonwoven may comprise a material thatprovides good recovery when external pressure is applied and removed.Further, according to one example, the nonwoven may comprise a blend ofdifferent fibers selected, for example from the types of polymericfibers described above. In some embodiments, at least a portion of thefibers may exhibit a spiral curl which has a helical shape. According toone example, the fibers may include bicomponent fibers, which areindividual fibers each comprising different materials, usually a firstand a second polymeric material. It is believed that the use ofside-by-side bi-component fibers is beneficial for imparting a spiralcurl to the fibers. Examples of potentially suitable curled or “crimped”bicomponent fibers and nonwovens formed from them are described in U.S.Pat. Nos. 5,382,400; 5,418,045; 5,707,468; 6,454,989, 6,632,386;5,622,772 and 7,291,239. For purposes herein, use of a nonwoven formedof crimped bicomponent or multicomponent fibers such as, for example,described in the patents cited immediately above, may be desired as oneboth layers 25 a, 25 b used to form the belt portions, because they canfeel particularly soft to the touch (for wearer comfort on the insideand aesthetically pleasing feel on the outside) and are generally quitepliable, making them easily drawn laterally at the lower rear leg edgesas will be described below.

In order to enhance softness perceptions of the laminate, nonwovens maybe treated by hydrojet impingement, which may also be known ashydroenhancement, hydroentanglement or hydroengorgement. Such nonwovensand processes are described in, for example, U.S. Pat. Nos. 6,632,385and 6,803,103, and U.S. Pat. App. Pub. No. 2006/0057921.

Other examples of nonwoven web that may be useful in the presentlaminate may be an SMS web (spunbond-meltblown-spunbond web) made byAvgol Nonwovens LTD, Tel Aviv, Israel, under the designation XL-S70-26;a softband SSS (spunbond-spunbond-spunbond) web made by Pegas NonwovensAS in Znojmo, Czech Republic, under the designation 18 XX 01 00 01 00(where XX=the variable basis weight); an SSS web made by Gulsan SentetikDok San VE TIC AS, in Gaziantep, Turkey, under the designation SBXXFOYYY(where XX=the variable basis weight, and YYY=the variable crossdirection width); an HESB (hydroenhanced spunbond) web made by FirstQuality Nonwovens Inc., in Hazelton, Pa., under the designationSEH2503XXX (where XXX=the variable cross direction width); and abicomponent SS web. Inclusion of a meltblown layer (such as in an SMSweb) may be desired because meltblown fibers, being much finer and ofgreater count per unit planar area, per unit basis weight, impartcomparatively greater opacity to a web, per unit basis weight, thanspunbond fibers. It may be desirable to utilize a nonwoven whichincludes a meltblown layer (such as an SMS web) for one or both of innerlayer 25 a and outer layer 25 b, wherein the added opacity providesbetter concealment of the wearer's skin at the sides/hips.

Generally, the basis weight of a nonwoven impacts its thickness,pliability and tensile strength. For two respective nonwovens formed ofotherwise identical types of fibers and through otherwise identicalprocesses, with the only difference being basis weight, the nonwovenwith the lesser basis weight will have a lower fiber count per unitplanar area, and be the thinner and more pliable of the two. Conversely,the nonwoven with the greater basis weight will have a greater fibercount per unit planar area, and will be the thicker and stiffer of thetwo. Generally, the nonwoven with the greater basis weight, having agreater fiber count, will also likely have the greater tensile strengthin the machine and cross directions.

A certain amount of machine and cross direction tensile strength isusually desired for processing; the nonwoven web must be able to sustaintensile loads imposed by processing equipment without tearing orexhibiting excessive deformation. Further, it may be desired that thenonwoven web portions of the belt structure impart a minimum lateraltensile strength to the belt at the limits of its ordinary stretch as inuse (i.e., when all ruffles or rugosities 27 are pulled out). On theother hand, for purposes of forming a belt structure as describedherein, a thinner and more pliable web may be desired for maximumbreathability (to keep the wearer's skin beneath the belt structurerelatively cool and dry) and comfortable fit. Maximum pliability is alsodesirable to facilitate lateral drawing back of the material at thelower rear leg edges as described below. Accordingly, selecting anappropriate basis weight involves finding an appropriate balance betweenthese competing concerns. It is believed that the basis weight of theinner layer 25 a is preferably selected to be from 7 gsm to 18 gsm, morepreferably from 8 gsm to 15 gsm, and still more preferably from 9 gsm to12 gsm. It is believed that the basis weight of the outer layer 25 b ispreferably selected to be from 10 gsm to 30 gsm, more preferably from 12gsm to 25 gsm, and still more preferably from 14 gsm to 20 gsm. It willbe understood that both layers 25 a and 25 b in combination add lateraltensile strength to the belt structure 23. The combined basis weight ofboth layers 25 a and 25 b (not including elastic strands) may beselected to be from 17 gsm to 48 gsm, more preferably from 20 gsm to 40gsm, and still more preferably from 23 gsm to 32 gsm. The respectivenonwoven materials used to form these layers may be selected to haveequal or differing basis weights. It may be preferred to have the innerlayer 25 a to have lower basis weight than that outer layer 25 b, toprovide greater pliability of the ruffles or rugosities 27 next to thewearer's skin, while providing a thicker appearance on the outside.

In a particular example, inner layer 25 a may be an SMS nonwoven asdescribed herein having a basis weight from 7 gsm to 18 gsm, and outerlayer 25 b may be formed predominately of multicomponent or bicomponent,crimped fibers as described herein, having a basis weight from 17 gsm to48 gsm.

Layers of nonwoven web 25 a, 25 b may sandwich one or more elasticmembers such as a plurality of strands 26 of an elastomeric material,such as an elastane (for example, LYCRA HYFIT fiber, a product ofInvista, Wichita, Ks). Layers of nonwoven web 25 a, 25 b may be joinedtogether about elastic strands 26 by adhesive deposited between thelayers, by thermal bonds, by compression bonds, or by a combinationthereof. In other examples, the one or more elastic members may bestrips or a section of film formed of elastomeric material.

The elastomeric members can also be formed from various other materials,such as but not limited to, rubbers, styrene ethylbutylene styrene,styrene ethylene propylene styrene, styrene ethylene ethylene propylenestyrene, styrene butadiene styrene, styrene isoprene styrene, polyolefinelastomers, elastomeric polyurethanes, and other elastomeric materialsknown in the art, and combinations thereof. In some embodiments, theelastic members can be extruded strand elastics with any number ofstrands (or filaments). The elastomeric members can have a decitexranging from 50 to 2000, or any integer value for any decitex value inthis range, or any range formed by any of these integer values. Theelastomeric members may be in a form of film. Examples of films havebeen described extensively in prior patent applications (see, forexample, U.S. Pat. App. Pub. No. 2010/0040826). The film may be createdwith a variety of resins combined in at least one of several sublayers,the latter providing different benefits to the film.

During manufacture of the belt structure, the elastic members such aselastic strands 26 may be pre-strained lengthwise by a desired amount asthey are being incorporated into the belt structure. Upon subsequentrelaxation of the belt, the elastic members such as elastic strands 26will contract toward their unstrained lengths. This causes the layers ofnonwoven material 25 a, 25 b to gather and form ruffles or rugosities 27having ridges 28 and valleys 29 generally transverse to the lengths ofthe elastic strands 26, and extending in the z-direction.

It may be appreciated that the size(s) and shape(s) of the rugosities 27will be affected, and may be manipulated, by design of the pattern ofjoined portions and/or bonding between the layers of nonwoven web 25 a,25 b, with respect to each other and with respect to elastic strands 26.When joining and/or bonding is effected using adhesive deposited uponone or both layers 25 a, 25 b prior to lamination, the adhesive may bedeposited in a pattern. Examples of methods for applying patterneddeposits of adhesive to a nonwoven web substrate to enable manufactureof an elasticized laminate are described in U.S. Pat. No. 8,186,296. Thepattern selected may be effected by design of a correspondingly designedroller. The pattern of adhesive to be applied may be designed to affectthe size(s) and shape(s) of the rugosities 27. The layers 25 a, 25 b maybe adhesively joined and/or bonded to each other at the locations ofadhesive deposits, and remain unjoined or unbonded, or free, of eachother at other locations, such that they may move and shift slightlyrelative each other as the laminate is moved and stretched, as duringwear of the article. Similarly, when joining and/or bonding is effectedusing thermal calender bonding, the joining and/or bonding pattern maybe designed to affect the size(s) and shapes of the rugosities 27.

In another example, to adhere the components of the belt laminate, theelastic strands 26 themselves may be individually coated with adhesive(“strand coated”) prior to incorporation into the belt laminate. Uponsubsequent lamination with layers 25 a, 25 b, this may be the primarymechanism of adherence or the layers 25 a, 25 b and the strands 26 tothe laminate structure, at least in the majority of the planar surfacearea of the belt laminate in the areas laterally outside the outerperimeter 41 of the central chassis 30 (i.e., in the side/hip areas).This may provide advantages in that any pre-strain imparted to theelastic strands during manufacture will be evenly, fixedly distributedlaterally to the layers 25 a, 25 b, promoting even formation and evenlateral distribution and even sizing of rugosities 27 upon relaxation ofthe assembled belt structure or portions thereof. Additionally, sincethe belt laminate may be thus formed with layers 25 a, 25 b unadhered tothe laminate except along the elastic strands 26, the layers 25 a, 25 bin the areas between the strands remain free to shift about and moveindependently of each other (including in the z-direction), providingadded pliability, flexibility and loft to the belt laminate, whichenhance wearer comfort and contribute to a luxurious look and feel.Strand coating in the lower half of the rear belt portion 23, or in thesection of the rear belt portion disposed below the seam 24 andlaterally outside the outer perimeter 41 of the central chassis 30, maybe particularly advantageous because the above-referenced evendistribution of elastic pre-strain, and pliability of the laminate, maybetter facilitate lateral drawing of the lower corner 21 a of the rearbelt portion 23 toward the central chassis 30, as will be describedbelow. Thus, it may be preferred that layers 25 a, 25 b in the majorityof the planar surface area of rear belt portion 23 laterally outside theouter perimeter 41 of the central chassis 30 and below seams 24 areadhered to the laminate along the elastic strands 26, but are unattachedto the laminate structure along all or a majority of intervening areas36, disposed laterally inward of seams 24, laterally outward of centralchassis 30, between strands 26 and above lower lateral belt edge 18.Various coating methods and techniques, including strand coating methodsand techniques, are shown for example in U.S. Pat. Nos. 5,340,648;5,501,756; 5,507,909; 6,077,375; 6,200,635; 6,235,137; 6,361,634;6,561,430; 6,520,237; 6,582,518; 6,610,161; 6,613,146, 6,652,693,6,719,846 and 6,737,102. The adhesive used may be a hot-melt typeadhesive having elasticity and flexibility making it suitable forattaching pre-strained elastic materials to substrates, such as OMNIMELTBLOCKS 22 H2401F, or ZEROCREEP brands such as AVANCÉ, available fromBostik, Inc., Wauwatosa, Wis.

Referring to FIGS. 2 and 6, it can be seen that rear belt portion 23 maybe made so as to be longer than front belt portion 22. This may bedesired to provide leg opening 15 edges that are higher in the front ofthe pant than in the rear of the pant to more comfortably accommodatethe wearer's forward bending of the legs at the hips (and reducingchanges of rubbing or chafing of the wearer's skin at the front legopening edges), while providing greater coverage of the wearer'sbuttocks at the rear. Considering FIG. 6, however, it can be seen thatmerely joining front 22 and rear 23 belt portions without some furthermodification will result in a leg opening edge that has a step profileto the rear of the side seam. When such a pant is worn, the areas of therear belt portion 23 lying below lines of leg opening tension 16(extending from the bottom extent of the side seam 24 to the point atwhich the rear belt portion 23 joins the chassis 30) including corner 21a may create an awkward or unsightly appearance. Portions of thematerial below lines of tension 16 may flip outward and/or curl, andthereby undesirably present a ragged, unfinished or haphazardappearance.

One solution to this problem is illustrated in FIGS. 7A and 7B. If, inmanufacture of the pant, a section of the rear belt portion 23 is cutaway along cut line 17 which may be approximately co-located along whatwould be the line of tension 16, the portions of the belt prone toflipping and/or curling are removed. The cut may also have any othersuitable profile desired. It will be appreciated, however, that cuttingaway portions of materials in this manner creates a need for cuttingequipment and a process, and generates cutoff scrap, which must beremoved from the manufacturing line and plant environment, and eitherrecycled or disposed of as waste. These necessities add cost andcomplexity to the manufacturing process.

An alternative solution may be described with reference to FIGS. 8A-8C.Rather than elastic strands 26 of uniform modulus, decitex and/orextents of prestrain being incorporated into rear belt portion 23,elastic strands disposed on the lower area of rear belt portion 23, suchas those disposed below seams 24, may have or may be imparted withdifferent features that cause them to impart differing lateralcontractive force(s), than the elastic strands above them.

In one example, one or more of the elastic strands disposed below a seam24 may vary by one or more of the extent of prestrain, tensile modulusor decitex. One or more of comparatively greater prestrain, greatertensile modulus and/or greater decitex (same material) will cause anelastic strand to exert comparatively greater contractive force alongits lateral length when elongated, as when the pant is worn. Thisgreater contractive force will tend to cause the areas of the rear beltbelt portion 23 about the elastic strand to be drawn laterally inwardly(toward the chassis 30) a comparatively greater distance, when the rearbelt portion is allowed to partially or entirely relax laterally. Thenonwoven layers 25 a, 25 b (see FIG. 5) will accommodate the greaterlateral contraction by forming comparatively more numerous or largerrugosities 27 along/about the elastic strand.

It can be appreciated, then, that a lower group of elastic strands 26 inthe rear belt portion, for example, a group disposed below a seam 24 (inthe examples depicted in FIGS. 8A-8C, elastic strands 26 a-26 d) may beselected and/or pre-strained to impart grouped, or individualized,successively lesser or greater lateral contraction forces, about theirlateral lengths, to the rear belt portion, to alter the profile assumedby the lower lateral belt edge 18 and side edge 19 lying below the seam24 and laterally outside the outer perimeter 41 of central chassis 30.In a simple example, the lateral contractive force exhibited by thecombination of the two lowermost elastic strands 26 in the rear beltportion (e.g., strands 26 a and 26 b in FIG. 8A) is greater than thelateral contractive force exhibited by the combination of the twouppermost elastic strands (e.g., strands 26 c and 26 d in FIG. 8A)disposed below seam 24, when the laminate is stretched to a uniformwidth. This may be accomplished by pre-straining the two lowermoststrands by a combined greater amount than the uppermost strands, duringmanufacture. It may also be accomplished through use of strands havingan average decitex greater for the two lowermost strands than for thetwo uppermost strands. For simplicity and reliability of manufacturingprocess, it may be preferred to use strands of differing decitex ratherthan to impart differing amounts of pre-strain/elongation to them duringmanufacture.

In another example, the amount of pre-strain of the lowermost elasticstrand imparted during manufacture of the pant (e.g., strand 26 a shownin FIG. 8A) is selected to be sufficiently high such that it cannotcontract fully to its relaxed length upon completion of manufacture andsubsequent relaxation of the belt structure, because sufficient materialin the layers 25 a, 25 b is present to prevent such full contraction.This will ensure that tension is always present in the lowermost rearportion of the belt structure 23, which draws and holds corner 21 alaterally inward toward the central chassis 30, even if the pant is wornby a relatively smaller wearer.

In another example, a lowermost strand in the rear belt portion (e.g.,strand 26 a shown in FIG. 8A) may be formed of the same elastomericmaterial but may have a decitex that is from 30% to 90%, more preferablyfrom 40% to 80%, and still more preferably from 50% to 70%, greater thanthat of a highest elastic strand 26 disposed below seam 24 (e.g., strand26 d shown in FIG. 8A). In one particular example, one or more elasticstrands disposed above the seam in the rear belt portion may be 940 dtexLYCRA strands, a first strand below the seam may be an 1100 dtex LYCRAstrand, and a lowermost strand nearest the lower lateral edge may be a1520 dtex LYCRA strand. (LYCRA strands are a product of Invista,Wichita, Kans.) If imparted with the same pre-strain during manufactureof the pant, these strands of differing decitex will impart differinglaterally contractive forces in belt structure during wear, with thegreater decitex strand imparting the greater laterally contractiveforce. It will be appreciated for this example, that the lowermoststrand will impart the greatest laterally contractive force. The resultwill be that the lowermost strand will tend to cause lower corner 21 aof the belt structure to be drawn laterally toward the center chassis30, as suggested in FIG. 8B. The ruffles or rugosities 27 will becomparatively more numerous or larger in the areas of greater lateralcontraction of the belt laminate.

The overall profile of the rear leg opening edge may be manipulated byvarying the decitex and/or pre-strain of the elastic strands 26 disposedbelow the seam 24 in other ways.

In the example illustrated in FIG. 8B, lowest elastic strand 26 a may beselected and/or prestrained to an extent that causes it to imposecontractive force along its lateral length that is equal to or greaterthan any of elastic strands 26 b, 26 c, 26 d, etc., which may tend tocause it to draw the areas of rear belt portion 23 lying along itslateral length toward the central chassis 30 by a distance equal to orgreater than those areas disposed above strand 26 a and below seam 24.Strands disposed above strand 26 a (e.g., strands 26 b, 26 c, 26 d) maybe selected and/or prestrained to extents that cause them to imposesuccessively less contractive force, causing them to draw areas of rearbelt portion lying along their lateral lengths successively lesserdistances toward the central chassis 30. As a result, lateral 18 andside 19 edges can be caused to define a generally convex profile, assuggested in FIG. 8B, when the pant is worn. With appropriate selectionand/or extent of prestrain of the elastic strands disposed below theseam 24, the profile can be made fairly smoothed, with any discontinuitythereof at lower corner of rear belt portion 23 minimized.

In another example, lowest two elastic strands 26 a, 26 b may have acombined greatest decitex, and next lowest two elastic strands 26 c, 26d may have a combined next greatest decitex that is less than thegreatest decitex but greater than the decitex of strands disposed abovethe next lowest two elastic strands. In one even more particularexample, the lowest two elastic strands and next lowest two elasticstrands, respectively, may be formed of LYCRA, have a decitex of 1520and 1100, respectively, and be prestrained at 290% when incorporatedinto the rear belt portion during manufacture thereof.

In another example illustrated in FIG. 8C, the elastic strands disposedbelow the seams 24 may be selected and/or prestrained so as to impart adiffering profile to the lower rear leg opening edges formed by edges18, 19, than that illustrated in FIG. 8B. In the example in FIG. 8C, oneor more of the elastic strands (e.g., strands 26 c, 26 d) lyingimmediately below a seam 24 may be selected and/or prestrained so as toimpart comparatively greater lateral contractive forces to the rear beltportion, than elastic strands below those (e.g., strands 26 a, 26 b).This may cause the rear belt portion to draw in laterally along adiffering, generally convex profile, as suggested in FIG. 8C.

To maximize the rear edge profile and corner 21 a smoothing effect, itmay be desirable to limit the spacing between the lowermost elasticstrands (e.g., strands 26 a, 26 b, 26 c, 26 d) in the rear belt portion.It may be particularly desirable that the spacing between the twolowermost strands (e.g., strands 26 a, 26 b) be no more than 10 mm, morepreferably no more than 9.0 mm, even more preferably no more than 8.0mm, and still more preferably no more than 7.0 mm. This helps ensurethat the ruffles or rugosities 27 in the layers 25 a, 25 b proximate thelower edge 18, resulting from lateral contraction of the elasticstrands, are controlled and kept relatively large in number, andconsequently, relatively small in size.

In conjunction with the configuration of elastic strands describedabove, it may be desired that the lowermost elastic strand (e.g., strand26 a in FIGS. 8B and 8C) be disposed no more than 5.0 mm, morepreferably no more than 4.0 mm, and even more preferably no more than3.0 mm, from the lower lateral edge 18 of the rear belt portion, atleast at lower corner 21 a. This will minimize the amount of nonwovenmaterial that is not controlled by an elastic strand, which mayotherwise contribute to creating a ragged appearance at the leg openingedges—particularly at lower corner 21 a.

Referring to FIG. 9, also in conjunction with the configuration ofelastic strands described above, it may be desired to impart bonding 40between layers 25 a, 25 b along edges 18, 19, of rear belt portion 23.Such bonding may serve to prevent any separation of the layers alongedges 18, 19 that may contribute to creating a ragged appearance, andmay also help the rear belt portion more effectively draw inwardlaterally toward the central chassis 30, under the contractive force ofthe elastic strands below seams 24. Bonding 40 may be effected bymechanical/compression bonds as described in, for example, U.S. Pat.Nos. 4,854,984 and 4,919,738, by thermal bonds or welds, or by depositsof adhesive between layers 25 a, 25 b. As suggested in FIG. 9, suchbonding may form a pattern along edges 18, 19. Such bonding may besupplemental to any bonding between layers 25 a, 25 b generally holdingrear belt portion 23 together as a laminate structure.

Side seams 24 may be permanent or refastenable. Permanent seams areformed between the front belt portion and the rear belt portion by anybonding mechanism wherein the front and rear belt portions may not beforcibly separated without damage to one or both of the front and rearbelt portions, or without any mechanism by which reattachment orrefastening may be effected. Bonding forming permanent seams may includecompression bonding, thermal bonding/welds or adhesive bonding.Refastenable seams are formed between the front belt portion and therear belt portion by any mechanism configured to permit substantiallynon-destructive forcible separation of the front and rear belt portions,and subsequent reattachment or refastening along the same location. Oneexample of such mechanism is a hook-and-loop fastening system, forexample, a VELCRO fastening system. A suitably sized and shaped hookscomponent may be bonded to one of the front or rear belt portions alongthe longitudinal edges thereof, and a suitable sized and shapes loopscomponent may be bonded to the other of the front or rear belt portionsalong the longitudinal edges thereof, in positions in which they may bebrought together and engaged to form seams 24.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

Every document cited herein, including any cross referenced or relatedpatent or application and any patent application or patent to which thisapplication claims priority or benefit thereof, is hereby incorporatedherein by reference in its entirety unless expressly excluded orotherwise limited. The citation of any document is not an admission thatit is prior art with respect to any invention disclosed or claimedherein or that it alone, or in any combination with any other referenceor references, teaches, suggests or discloses any such invention.Further, to the extent that any meaning or definition of a term in thisdocument conflicts with any meaning or definition of the same term in adocument incorporated by reference, the meaning or definition assignedto that term in this document shall govern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. A disposable absorbent pant, comprising a frontbelt portion, a rear belt portion and a central chassis having an outerperimeter, a front region, a crotch region, a rear region, a topsheet, abacksheet and an absorbent core disposed between the topsheet and thebacksheet, the central chassis being joined to the front belt portion inthe front region, and being joined to the rear belt portion in the rearregion, wherein the rear belt portion has a greater length than thefront belt portion and the front belt portion is joined to the rear beltportion along respective left and right side seams; wherein a lower edgeof the rear belt portion forms at least in part edges of left and rightleg openings to the rear of the respective left and right side seams,and the rear belt portion comprises: first and second layers comprisingfirst and second nonwoven web materials; and a plurality oflongitudinally-spaced, pre-strained, laterally-oriented elastic strandssandwiched between the first and second layers and disposed below theside seams; wherein a first of said plurality of elastic strands differsfrom a second of said plurality of elastic strands disposed above thefirst, by having one or more of comparative contractive force increasingfeatures selected from the group consisting of: greater pre-strain,greater tensile modulus, and greater decitex, and combinations thereof;and wherein the first nonwoven web material has a first basis weightfrom 7 gsm to 18 gsm, more preferably from 8 gsm to 15 gsm, and stillmore preferably from 9 gsm to 12 gsm; and the second nonwoven webmaterial has a second basis weight from 10 gsm to 30 gsm, morepreferably from 12 gsm to 25 gsm, and still more preferably from 14 gsmto 20 gsm.
 2. The pant of claim 1 wherein a first group of saidplurality of elastic strands differs from a second group of saidplurality of elastic strands disposed above the first group, by havingone or more of comparative contractive force increasing featuresselected from the group consisting of: greater combined pre-strain,greater combined tensile modulus, and greater combined decitex, andcombinations thereof.
 3. The pant of claim 2 wherein the first groupcomprises at least 2 elastic strands.
 4. The pant of claim 2 wherein alowest elastic strand of said first group differs from a next lowestelastic strand of said first group, by having one or more of comparativecontractive force increasing features selected from the group consistingof: greater pre-strain, greater tensile modulus, and greater decitex,and combinations thereof.
 5. The pant of claim 1 wherein a lowest ofsaid plurality of elastic strands has one or more of comparativecontractive force increasing features selected from the group consistingof: greater pre-strain, greater tensile modulus, and greater decitex,and combinations thereof.
 6. The pant of claim 1 wherein the pre-strainand tensile modulus of all of the plurality of elastic strands areapproximately the same.
 7. The pant of claim 1 wherein the edges of theleft and right leg openings formed by the rear belt portion define agenerally convex profile when the pant is worn by a wearer.
 8. The pantof claim 1 wherein each of the plurality of elastic strands has apre-strain, and a lowest of said plurality of elastic strands does notcontract to its unstrained length when the rear belt portion is relaxed.9. The pant of claim 1 wherein a lowest of said plurality of elasticstrands is disposed no more than 5.0 mm, more preferably no more than4.0 mm, even more preferably no more than 3.0 mm from said lower edge ofsaid rear belt portion, at a lower corner of said rear belt portion. 10.The pant of claim 1 wherein a lowest of said plurality of elasticstrands is spaced from a second lowest of said plurality of elasticstrands by no more than 10 mm, more preferably no more than 9.0 mm, evenmore preferably no more than 8.0 mm, and still more preferably no morethan 7.0 mm.
 11. The pant of claim 10 wherein the second lowest of saidplurality of elastic strands is spaced from a third lowest of saidplurality of elastic strands by no more than 10 mm, more preferably nomore than 9.0 mm, even more preferably no more than 8.0 mm, and stillmore preferably no more than 7.0 mm.
 12. The pant of claim 1 whereinsaid side seams are permanent.
 13. The pant of claim 1 wherein one orboth of said side seams is refastenable.
 14. The pant of claim 1 whereinlongitudinal edges of the rear belt portion disposed below the sideseams comprise edge bonding between the first and second layers.
 15. Thepant of claim 1 wherein lower lateral edges of the rear belt portiondisposed laterally outside the outer perimeter of the central chassiscomprise edge bonding between the first and second layers.
 16. The pantof claim 1 wherein at least one of the first and second nonwoven webmaterials comprises meltblown fibers.
 17. The pant of claim 1 wherein atleast one of the first and second nonwoven web materials comprisesbicomponent fibers.
 18. The pant of claim 1 wherein at least one of thefirst and second nonwoven web materials comprises an SMS material. 19.The pant of claim 1 wherein the first layer is an inner layer and thefirst nonwoven web material comprises an SMS material.
 20. The pant ofclaim 1 wherein one or more of the plurality of elastic strands has beenstrand coated with adhesive during manufacture of the rear belt portion.21. The pant of claim 20 wherein the first and second layers are notadhered to each other over a majority of the planar surface area of therear belt portion disposed below the side seams and laterally outsidethe outer perimeter of the central chassis.